Modern CPUs are seated in zero-insertion force (ZIF) sockets. These have locking levers, so don't try to pull up the CPU cooler with the CPU still attached. The right way is to unplug the CPU fan, remove the heatsink/fan, then raise the ZIF lever to release the CPU, and very carefully lift it out. Most likely there is a coating of thermal paste between the heatsink and CPU, and this can make it difficult to separate the two. First run your PC for a few minutes to warm everything up. Then turn it off. Release the heatsink latches, then carefully twist and lift it to break free from the thermal paste. Thermal paste is not an adhesive, but it does get gummy over time.

Now raise the ZIF lever, and the CPU should lift out easily. Do not bend or break any of the pins, or damage the socket. Bent CPU pins can usually be bent back into place, broken pins are fatal.

Old gummy CPU with the heatsink removed

Next, clean the CPU and heatsink thoroughly. Use a credit card or plastic putty knife to scrape off the thermal paste. Then use plain old isopropyl alcohol (or the special cleaning fluid) and a lint-free cloth to remove the remainder. Never ever use anything that will leave scratches. Finally, give them a good polish with a microfiber cloth until they are perfectly clean.

Nice cleaned up CPU, all gunk gone

Installing the New CPU and Heatsink

Clean the top of your new CPU the same way as cleaning an old one. Your new CPU will fit only one way, which you can tell by comparing the pin pattern to the motherboard socket on AMD processors, and matching the tabs on Intel CPUs. Raise the ZIF lever, then carefully place the CPU in the socket. If it doesn't drop in with no force, it's going the wrong way. Once it is correctly seated, lower the lever to lock it into place.

Pins on AMD CPUs have a matching pattern on the motherboard socket, to show the correct orientation

If you have a new CPU cooler, it probably comes with a pad of thermal paste already applied. In my experience a good thermal paste like Arctic Silver does a better job. If you want to use a different paste, thoroughly clean off the old paste first. Then apply the new paste in the correct way, not the wrong way, which seems to be endemic. (See below for the right way.)

Stock AMD heatsinks are easy; these have two latches. Hook the back one first, then the front latch, which is the one with the lever, then carefully flip the lever into the locking position.

Intel heatsinks have four feet; each one presses into place, then has its own little lock.

Thermal Paste Misconceptions

I was amazed to find so much terrible and wrong thermal paste information on the Web. If CPUs and heatsinks had perfectly-machined, flat surfaces then thermal paste would be unnecessary. The goal is to have perfect, uniform heat transfer. The job of the thermal paste is to fill in any microscopic defects and provide that flat, uniform surface. So the last thing you want to do is glop it all over your CPU; all that is required is a very tiny bit. Arctic Silver, which is my personal favorite thermal paste, advises placing a small dot in the center of the CPU. Then the pressure of clamping the CPU and heatsink together, and the heat of operation will spread it out uniformly. They say that after a break-in period of 200 hours CPU temperature should drop 2C-5C.

Final Checklist

Make triply-certain that all of your fans are plugged in---case fans, and especially the CPU fan. I know, you would never miss such an obvious step, but some of us do! Then fire it up and see what happens. It should Just Work.

Measuring CPU Temperature

There are several ways to measure CPU temperatures. I like to boot into the system BIOS, navigate to the section that shows system health, and leave it running for a couple hours. Motherboard sensors are not always accurate, but it's worth a look-see. You may also have options to set warnings and automatic shutdowns when it reaches dangerous temperatures.

Come back next week for part 3, where we'll learn how to monitor CPU temperatures and performance using nice ordinary Linux utilities.

Carla Schroder is the author of the Linux Cookbook and the Linux Networking Cookbook (O'Reilly Media), the upcoming "Book of Audacity" (NoStarch Press), a lifelong book lover, and the managing editor of LinuxPlanet and Linux Today.